1. Field of the Invention
The present invention relates to a self-compacting engineered cementitious composite and method for making the same, and more preferably a self-compacting hydrophilic fiber/engineered cementitious composite and method for making the same.
2. Background Art
Many buildings and other load bearing structures are constructed with cementitious materials, such as concrete and cement. However, conventional concrete or cement materials tend to be brittle and, as such, tend to be relatively susceptible to failing in a catastrophic manner when subjected to tensile loading. To overcome this shortcoming, engineered cementitious composites (ECC) have been developed. ECCs are high ductility and high toughness cementitious composites and comprise a modified cement containing small amounts of short reinforcing fibers. The superior ductility and high toughness of ECC materials allows the ECC materials to be used in demanding structures where severe loading or high deformation is imposed, such as in construction facilities subjected to seismic loads. ECCs have also been used or are currently being investigated for use as materials for building and/or civil engineering structures, such as walls, floors, flat slabs, support beams and columns, as well as for manufactured elements, such as extruded pressure pipes and tubing.
Due to the poor fluidity of fresh concrete, the placing and casting of concrete in the field generally requires a considerable amount of vibration and consolidation. Moreover, there are cases, such as when using formworks with complicated and congested reinforcement or those with unusual geometries, that normal vibration and consolidation are difficult or even impossible to be conducted. If concrete is not properly compacted, gaps, voids, and/or cracks can be formed in the resulting concrete structure thereby significantly affecting the performance (the constructionability and reliability) of the concrete structure.
Even in situations where the concrete can be properly compacted with the use of vibration and other external compaction methods, the noise, construction time, and cost generated from these techniques is considerable and undesirable. As can be readily understood, the inclusion of any fibrous materials into concrete makes the concrete material more difficult to compact, thereby typically requiring additional vibration over that necessary for concrete compositions that are essentially similar except for the inclusion of fibrous material. ECC containing hydrophobic, high performance polyethylene fibers have been prepared previously. However, such PE fibers are very expensive.
Accordingly, it would be desirable to provide a concrete material that has higher ductility and toughness than ordinary concrete while at the same time is able to flow under its own weight and fill in the framework in cast processing without a need for significant, if any, external vibration, i.e., is self-compacting, and which can use less expensive fibers in its preparation.
The present invention pertains to self-compacting engineered cementitious compositions containing a small volume proportion of non-hydrophobic fibers.